Synthesis and characterization of two-dimensional Nb4C3 (MXene).

We report on the synthesis of a phase-pure, 2-dimensional transition metal carbide Nb4C3, produced by immersing Nb4AlC3 powders in hydrofluoric acid. The structure of this, only second MXene with formula M4X3, was investigated with pair distribution function analysis. The resistivity of a cold-pressed disc was 0.0046 Ω m, rendering this MXene one of the most conductive to date.